Vacuum check valve

ABSTRACT

Resilient side loading of vacuum brake booster check valves to inhibit valve pulsations and resulting valve noises generated by pulsations from the vacuum source achieved by a single spring member functioning as a valve closing spring and as a lateral biasing spring acting on the valve.

This is a division of U.S. patent application Ser. No. 909,738, entitled"Vacuum Check Valve" filed Sept. 19, 1986 now U.S. Pat. No. 4,724,867

The invention relates to a vacuum check valve and more particularly tosuch a valve used in the vacuum supply line as a control for a vacuumsuspended brake booster supply. It is an improvement on the vacuum checkvalve of U.S. Pat. No. 4,628,959 entitled "Vacuum Check Valve", filedAug. 30, 1985, issued Dec. 16, 1986 and assigned to the common assignee.The valve assembly embodying the invention herein disclosed and claimedinhibits pulsation of the valve member as the vacuum pressures change,thus inhibiting the generation of undesirable valve noises.

Vacuum check valves of the type disclosed in U.S. Pat. No. 3,086,544,entitled "Check Valve " and issued Apr. 23, 1963, have been used withvacuum suspended power brake boosters for many years. The typical valveconstruction has a valve element positioned in a valve chamber and madeessentially of a washer and a rubber element. The valve is contained andguided within the chamber by the chamber side wall in relation to theouter periphery of the washer. A spring in the valve chamber urges thevalve element toward engagement with an annular ridge which forms avalve seat around the point of entry of the inlet conduit into the valvechamber. Since air flow must pass around the valve when it is open, theguiding function of the chamber side wall permits some valve lateralmovements so that the valve may not always be completely axially alignedwith the valve seat. This loss presented no problem with small leaksthat occasionally occur when used with larger engines. It has beenfound, as vehicle engines have been made smaller to achieve a higherfuel economy, less vacuum is available to operate various vehicleaccessories than was the case with most vehicle engines when such checkvalves began to be used.

The improved vacuum check valve in which the invention is preferablyincorporated is a guided poppet valve having a valve stem extendingthrough valve housing guide means. The poppet valve is reinforced forimproved sealability. The valve member seal which is engageable with thevalve seat is made of a material which substantially eliminates coldweather sticking. It minimizes the formation of ice crystals between thevalve seal and the valve seat so that leakage of air past the valve doesnot normally occur, even in extremely cold weather. The material is alsoof a type that has improved fuel resistance. By guiding the valve poppetwith a valve stem located along the valve poppet axis, greater clearanceis able to be maintained between outer periphery of the valve poppet andthe adjacent inner wall of the valve housing, permitting much higher airflow rates which are subject to substantially less restriction to flow.At the same time, the valve is maintained in proper guided relation tothe valve seat. This valve has now been accepted and is in productionuse with a large portion of the vacuum boosters made in the UnitedStates.

In the improved vacuum check valve, the valve member is laterally biasedby a spring element which is an integral part of the valve closingspring. This bias causes a slight drag force to be exerted on the valvemember which is sufficient to inhibit valve member pulsations whilepermitting proper valve operation. Other advantages are set forth below.

IN THE DRAWINGS

FIG. 1 is a cross-section view with parts broken away and illustrating avacuum check valve embodying the invention.

FIG. 2 is a fragmentary cross-section view, with parts broken away,illustrating the vacuum check valve of FIG. 1 taken in the direction ofarrows 2--2 of that figure.

FIG. 3 a perspective view of the spring of FIGS. 16 and 17.

The system 20 shown in FIG. 1 includes an engine intake manifold 22. Asis well known, the intake manifold of an internal combustion engine iscommonly used as a source of vacuum to supply vacuum pressure to certainaccessories. A suitable connection 24 is provided to tap into the intakemanifold and obtain vacuum therefrom.

A vacuum suspended brake booster servomotor may be the device with whicha check valve embodying the invention is used, as more fully disclosedin the above noted patents. The servomotor has a vacuum check valveassembly 26 mounted on the servomotor housing front section 28 andopening at one side into the servomotor vacuum chamber 30. The otherside of the vacuum check valve assembly 26 is connected by the vacuumconnection 24 to the intake manifold vacuum source 22.

An example of the servomotor, with a more detailed description of itsoperation, is found in U.S. Pat. No. 3,249,021, issued May 3, 1966 andentitled "Power Brake Booster".

The vacuum check valve assembly 26 of FIG. 1 includes a housing 54formed of housing sections 56 and 58. Housing section 58 is sealinglysecured to housing section 56 somewhat like a cover and cooperates withhousing section 56 to define a valve chamber 60. An inlet 62 isintegrally formed with housing section 56. The inlet is constructed toalso provide means to secure the valve assembly to the housing frontsection 28 through a booster housing front section opening 64 in sealingrelation. An outlet 66 is also formed as a part of housing section 56and is arranged to receive vacuum connection 24 in sealing relation toprovide communication between the valve outlet 66 and the vacuum source22. The inlet and outlet passages respectively defined by inlet 62 andoutlet 66 each connect with the valve chamber 60. Housing section 56also has a web 68 formed therein over the passage formed by inlet 62,the web being provided with web openings 70 which provide asubstantially unrestricted fluid flow connection from the inlet 62 intothe valve chamber 60. Web 68 has a center part 72 which is in axialalignment with the inlet 62. An opening 74 is formed axially through theweb center part 72 so that the web center part forms a guide for thevalve member to be described. An annular valve seat 76 is defined by asurface formed as a part of housing section 56 and generally defining anend wall of the valve chamber 60 together with web 68. The surface ofweb center part 72 facing toward the main portion of the valve chamber60 may be a planar extension of the surface defining the annular valveseat 76.

Valve housing section 58 is provided with a boss 78 extending into thevalve chamber 60. Boss 78 has a recessed opening 80 formed therein andopening into the valve chamber 60. Opening 80 is in axially spacedalignment with the web opening 74. Boss 78 has a shoulder 82 formedaround its base and providing an engagement surface for a part of thevalve spring to be described. The end 84 of boss 78 terminates in spacedrelation to the web center part 72. Recessed opening 80 also acts as aguide for a portion of the valve member to be described.

The check valve member 86 is a poppet type of check valve and iscontained within the valve chamber 60. Valve member 86 has a rigid valvemember body 88 formed to include a disc-like center section 90 and avalve stem arrangement defined by a first valve stem portion 92extending axially from one side of the center section 90 and forming afirst guided valve portion which is reciprocably received and guided byrecessed opening 80 of housing section 58. The stem arrangement includesa second valve stem portion 94 extending axially from the other side ofthe valve member center section 90 and forming a second guided valveportion. Valve stem portion 94 extends through the web opening 74 forguided reciprocal movement therein. One of the valve stem portions islarger in diameter than the other, and the same is true of the openings74 and 80, thereby preventing the valve member 86 from beingaccidentally assembled in the axially reversed position from thatdesired. For this purpose it is preferred that the valve stem portion 94and web opening 74 have a smaller diameter than that of the valve stemportion 92 and the recessed opening 80. Since the usual manner ofassembly of the valve in the housing would be to first insert stemportion 94 through web opening 74, it is clear that the larger valvestem portion 92 could not be so inserted because web opening 74 issmaller in diameter than that valve stem portion. This effectivelyprevents misassembly of the valve member in the housing.

Valve member 86 has a valve member seal 96 secured to the peripheralportion of the disc-like center section 90 of the valve body 88. Oneside of the annular valve member seal 96 has a valve seat-engageablesurface 98. Seat-engageable surface 98 is the outer end of acircumferentially formed valve member bead 100 which extends axiallyfrom the main part of the valve member seal 96 so as to be engageablewith the annular valve seat 76 of housing section 56. A valve springmember 180 is received in valve chamber 60 and has an inner base 186fitting about and engaging valve stem portion 92 and also engaging valvemember center section 90 in axially biased relation so that the valvemember 86 is continually urged toward surface sealing engagement withthe annular valve seat 76. Spring member 180, and particularly its innerbase 186, is so proportioned, and the axial distance between theshoulder 82 of boss 78 relative to the facing surface 196 of the springinner base 186 is such, that the valve member body may move against theforce of the spring 180 to fully open the valve by separating the valvemember bead 100 from the annular valve seat 76 a sufficient axialdistance to provide substantially no flow restriction past the bead andvalve seat. At the same time, stem 94 remains guided within the webopening 74 and valve stem 92 moves further into the recessed opening 80.The rigid valve member body 88 extends radially outward so that it isaxially aligned with the major portion of the valve member bead 100 toprovide reinforcement for the entire valve member seal 96 and axialstability for the valve member bead 100, thereby insuring planar sealingaction of the bead 100 with the valve seat 76. The guiding action ofopenings 74 and 80 on stem portions 94 and 92, respectively, furtherassure the maintenance of the sealing surface of the valve member seal96 in parallel planar relation with the valve seat 76 at all times.

When the valve member bead 100 is in sealing engagement with seat 76 asshown in FIG. 1, the valve chamber 60 is separated into a chamber inletsection 104 and a chamber outlet section 106. Chamber inlet section isin fluid communication with the inlet 62 so that the entire surface areaof the valve member 86 positioned radially inward of the seat engageablesurface 98 is exposed to pressure within inlet 62 and therefore thepressure in the vacuum chamber 30 of the booster 28. The chamber outletsection 106 is in full fluid communication with the outlet 66 at alltimes, and the pressure therein is the pressure being transmitted to thecheck valve assembly 26 from the engine vacuum source 22 through vacuumconnection 24. This pressure also acts on the valve member 86 across thesame effective surface as that described immediately above for the inletpressure. It also acts on the small annular seat engaging surface area108 which is defined by the area through which surface 98 is in surfaceengagement with the annular valve seat 76. Therefore the pressure actingon valve member 86 and contained within chamber outlet section 106 actsover a slightly larger effective area than does the inlet pressureacting in the chamber inlet section 104 on the effective area of valvemember 86. This difference in effective areas is maintained at a minimalamount by keeping the area of surface 108 to a minimal amount. Theminimal contact area is also important in preventing the valve fromsticking during extremely cold conditions, as will be further described.

The valve member seal 96 of the construction shown in FIG. 1 ispreferably molded in place on the valve member body. It has been foundthat it is also preferable to make the valve member seals from afluoro-silicone rubber for improved fuel vapor resistance andminimization of cold weather sticking. The material should have adurometer of about 40 to 50 at a standard temperature of 70° F., andshould increase in durometer with a decrease in ambient temperature tono more than about 60 to 70 durometer at about minus 20° F. This willnot only substantially eliminate cold weather sticking of the valve sealto the valve seat under cold weather conditions, but will also maintaingood sealing characteristics throughout the range of temperaturesnormally encountered in vehicles, such a temperature range being from ashigh as about 280° F. in the engine compartment in which the valve isnormally located to as low as about minus 40° F.

By arranging the valve member so that it is guided and supportedaxially, greater clearance around the outer periphery of the valvemember in relation to the valve housing is permitted so to minimize flowrestriction in that area. It is preferred that the annular area definedby the outer periphery of the valve member and the portion of the valvehousing which is radially outward of the valve member outer periphery beat least as great as the effective cross-section area of the inlet portformed by inlet 62. This assures a substantially unrestricted air flowpast the outer periphery of the valve member when the valve assembly isopen. A considerably greater air flow may be obtained through the valvethan has heretofore been the case. This therefore leads to an increasein the size of vacuum hose such as vacuum connection hose 24, as well asthe sizes of the inlet 62 and the outlet 66, to take full advantage ofthe decrease in restriction to flow in the valve itself. This hasresulted in substantially less pressure drop in relation to flow rate,minimizing the amount of time required to reestablish the desired vacuumpressure in the vacuum chamber of the brake booster during or afterbooster operation. At the same time, the average differential pressurefor opening the vacuum check valve is maintained at less than one inchof mercury. Where the average flow restriction at a flow rate of 500cubic feet per hour of air through the valve has previously been in therange of about 18 to 28 inches of mercury, the valve as shown in FIGS. 1and 2 has an average flow restriction at this flow rate of less than 3inches of mercury. The valve has also minimized the amount of leakagewhen the valve is supposed to be fully closed. It has been equal to thebest of valves in current production at moderately high temperatures.For example, at 212° F., tests have indicated that no leakage hasoccurred, while on some production units, as much as 20% of the valveswill have some leakage at this temperature. It has considerablydecreased the valve leakage at cold temperatures, as well as valvesticking under cold temperatures. For example, the illustrated valve hadno leaks and did not stick at 0° F. The valve also showed dramaticimprovement in leakage and potential failure with a pressuredifferential thereacross as small as 2 inches of mercury and up to 20inches of mercury, in comparison to various valves used by differentmanufacturers.

It has been found that in some installations the valve of U.S. Pat. No.4,628,959 referred to above, would pulsate and generate disagreeablevalve noises. Experience indicated that this has occurred when used withsome engines but not with others. Therefore it is an object of theinvention herein disclosed and claimed to inhibit such pulsations andtherefore inhibit the generation of such undesirable valve noises. Onesuch embodiment is illustrated in FIGS. 1, 2 and 3.

The valve spring and the laterally biasing spring element are integrallyformed by the spring member 180 received in valve chamber 60. Member 180has an annular outer base 182 secured in the valve chamber 60 andparticularly in the valve chamber portion adjacent the valve housingsection 58. The securing arrangement may be by an interference or pressfit of the annular base 182 in a part of the valve housing section 56,with a shoulder 184 being provided to locate the axial position of thespring base 182. Annular outer base 182 is therefore positioned inradially spaced relation about valve stem 92. The spring member 180 hasits annular inner base 186 provided with an opening 188 through whichvalve stem 92 is received. When assembled on the valve stem 92, theinner base 186 has its axis 190 coincident with the axis 192 of valvestem 92. However, in its free state it is preferred that the axis 190 beparallel to axis 192 but laterally spaced slightly therefrom so that theannular inner base is biased laterally when it is in the installedposition. The bias is accomplished by a spring section 194 which joinsthe inner base 186 to the outer base 182. Spring section 194 isillustrated as being spirally formed so that it not only produces alateral bias but also produces an axial bias of the inner base 186relative to the outer base 182. The axial bias is transmitted to thevalve member 86 where the inner base fits about valve stem 92immediately adjacent the disc-like section 90 of the valve member.

The unitary spring member 180 therefore provides the continuous urgingof the inner base and the valve member toward the annular valve seat andalso continuously biases the inner base laterally against the valve stem92, creating sufficient drag of the valve stem in recess 80 to inhibitvalve pulsations and therefore inhibit the generation of undesirablevalve noises as above described.

The invention effectively inhibits valve pulsations when they are likelyto occur because of pressure differential changes at either the inlet oroutlet port or both, and therefore inhibits undesirable valve noisesgenerated as a result of such pulsations.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A vacuum check valveassembly for controlling vacuum fluid pressure in a container, saidcheck valve assembly comprising:a housing, a valve chamber in saidhousing defined by opposed end walls and a side wall formed as a part ofsaid housing, an inlet port and an outlet port formed in said housingand respectively opening through different ones of said walls so as tobe in fluid communication with said valve chamber, said inlet port beingadapted to be connected to a container in which vacuum fluid pressure isto be normally retained and said outlet port being adapted to beconnected to a source of vacuum fluid pressure, an annular valve seatformed as a part of one of said housing end walls about said inlet port,a valve member movably mounted in said valve chamber and having adisc-like valve section in radially inwardly spaced relation to saidchamber side wall, said valve member further having valve stem meansextending axially from said disc-like valve section, said housing havingvalve stem-receiving guide means formed in said opposed end wallslimiting the movements of said valve member to movements axially of saidvalve stem means and said disc-like valve section and toward and awayfrom said annular valve seat to close said inlet port in one positionand to open said inlet port and permit fluid flow around said disc-likevalve section through said valve chamber and into said outlet port, asingle spring member formed by a valve spring axially biasing said valvemember toward said annular valve seat and a spring element operativelyresiliently and laterally engaging said valve member and said housingand continuously biasing said valve member laterally, said single springmember having an annular outer base secured in said valve chamber inradially spaced relation about one of said valve stem means, an annularinner base with said one valve stem means received therethrough andengaging the disc-like portion of said valve member, and at least onespirally formed spring section joining said inner and outer bases andcontinuously urging said inner base and said valve member toward saidannular valve seat and also continuously biasing said inner baselaterally against said one valve stem means causing said valve stemmeans to drag and resist movements of said valve member and thuspreventing undesired valve member pulsing movements and consequent valvemember-generated noises during pulse-like changes of fluid pressure atat least one of said inlet and outlet ports.
 2. A vacuum check valveassembly for controlling vacuum fluid pressure in a container, saidcheck valve assembly comprising:a housing, a valve chamber in saidhousing defined by opposed end walls and a side wall formed as a part ofsaid housing, an inlet port and an outlet port formed in said housingand respectively opening through different ones of said walls so as tobe in fluid communication with said valve chamber, said inlet port beingadapted to be connected to a container in which vacuum fluid pressure isto be normally retained and said outlet port being adapted to beconnected to a source of vacuum fluid pressure, an annular valve seatformed as a part of one of said housing end walls about said inlet port,a valve member movably mounted in said valve chamber and having adisc-like valve section in radially inwardly spaced relation to saidchamber side wall, said valve member further having valve stem meansextending axially from said disc-like valve section, said housing havingvalve stem-receiving guide means formed in said opposed end wallslimiting the movements of said valve member to movements axially of saidvalve stem means and said disc-like valve section and toward and awayfrom said annular valve seat to close said inlet port in one positionand to open said inlet port and permit fluid flow around said disc-likevalve section through said valve chamber and into said outlet port, asingle spring member formed by a valve spring axially biasing said valvemember toward said annular valve seat and a spring element operativelyresiliently and laterally engaging said valve member and said housingand continuously biasing said valve member laterally, said single springmember having an annular outer base secured in said valve chamber inradially spaced relation about one of said valve stem means, an annularinner base with said one valve stem means received therethrough andengaging the disc-like portion of said valve member and having an axiswhich in its installed position is coincident with the axis of said onevalve stem means but in its free state is parallel to but laterallyspaced from that axis, and at least one spirally formed spring sectionjoining said inner and outer bases and continuously urging said innerbase and said valve member toward said annular valve seat and alsocontinuously biasing said inner base laterally against said one valvestem means causing said valve stem means to drag and resist movements ofsaid valve member and thus preventing undesired valve member pulsingmovements and consequent valve member-generated noises during pulse-likechanges of fluid pressure at at least one of said inlet and outletports.